Passenger&#39;s weight measurement device for vehicle seat and attachment structure for load sensor

ABSTRACT

There is disclosed a passenger&#39;s weight measurement device for a vehicle seat, capable of suppressing generation of an initial load. The passenger&#39;s weight measurement device includes an upper rail disposed to be movable back and forth on a lower rail fixed to a vehicle floor; a load sensor fixed on the upper rail; and a frame disposed on the load sensor and below a vehicle seat, wherein a rod extends from the load sensor to penetrate the frame and to be inserted into an insertion hole formed in a center of a leaf spring, the leaf spring is curved into an angle shape to separate the center of the leaf spring from the frame, a nut is engaged with the rod on the leaf spring, and both hems of the leaf spring abut on the frame in a state that the leaf spring is fastened by the nut.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a passenger's weight measurement devicefor vehicle seat, for measuring a weight of a passenger of a vehicleseat, and an attachment structure for attaching a load sensor to thepassenger's weight measurement device.

2. Description of the Related Art

Recently, to improve performance of various safety devices such as aseat belt and an air bag, operations of the safety devices have beencontrolled in accordance with a weight of a passenger sitting on avehicle seat in some cases. In the conventional passenger's weightmeasurement device for measuring a weight of a sitting passenger, a loadsensor is disposed between a vehicle floor and the vehicle seat (Forexample, refer to JP A 2004-317285 and U.S. Pat. No. 6,161,891).

However, when the passenger's weight measurement device is assembled,when the vehicle seat is fixed to the passenger's weight measurementdevice, and when the passenger's weight measurement device is fixed tothe vehicle floor or the like, a dimension error or an assemblingposition error occurs to cause very low distortion. Because an initialload is applied to the load sensor by the distortion, there is a firstproblem that it is difficult to accurately measure the passenger'sweight.

JP A 11-304579 discloses a passenger's weight measurement device capableof simplifying characteristics of a load applied on a load sensor asmuch as possible.

The passenger's weight measurement device disclosed in JP A 11-304579 isequipped with a seat connection mechanism which includes an arm disposedto interconnect a seat bracket and a seat of a vehicle and to rotate upand down. The device also includes a load sensor disposed between thevehicle and the seat to detect a seat weight. The arm is pivotallyattached to a pivotal shaft (pivot) of the seat side and a pivot of acar body side, and the load sensor selectively receives an up-and-downdirection component of the seat weight applied on the arm. According tothe passenger's weight measurement device disclosed in JP A 11-304579,displacement of the seat with respect to the vehicle body, which iscaused when a load is applied on the seat, has certain regularity, andcharacteristics of the load applied on the load sensor are simplified,thereby facilitating capturing of the passenger's weight on the seat.

According to the passenger's weight measurement device disclosed in JP A11-304579, seat adjusters project from four positions, front, back, leftand right, of a bottom surface of a seat cushion on which the passengersits. The seat adjuster is a portion of which a seat frame partiallyprojects, and can slide back and forth on a pair of seat rails bypassenger's adjustment. The seat adjuster and the seat rails constitutea so-called slide rail. However, the passenger's weight measurementdevice disclosed in JP A 11-304579 has a problem that the large numberof components such as a linking member is increased because the pair ofslide rails and the seat bracket fixed to the vehicle body floor sideare linked together by a parallelogram linking mechanism. Because theparallelogram linking mechanism is disposed between the pair of sliderails and the seat bracket, there is a problem that it is difficult toset a height from the vehicle body floor to an upper surface of the seatcushion equal to or less than a certain height.

To solve the aforementioned problems, a plurality of compression typeload cells (load sensors) are disposed between the pair of slide railsarranged on the vehicle body floor side and the pair of side frames forsupporting the seat. Thus, the configuration is simplified and therestrictions on the height from the vehicle body floor to the uppersurface of the seat cushion are eliminated. However, generally it isdifficult to accurately fix the pair of slide rails and the like to thevehicle body floor side. Further, it is difficult to maintain a facingdistance between the pair of side frames because of the seat sliding. Inthis structure, there is a second problem that an unnecessary force isapplied on the load cell to interfere with passenger's load measurement.

SUMMARY OF THE INVENTION

In connection with the first problem, it is an object of the presentinvention to provide a passenger's weight measurement device for avehicle seat, and an attachment structure for a load sensor, capable ofsuppressing generation of an initial load.

In connection with the second problem, it is another object of thepresent invention to provide a passenger's weight measurement devicewhich includes a pair of slide rails and load cells arranged at fourcorners of the slidable seat and which can prevent interference withload measurement of the load cells.

In accordance with a first aspect of the present invention, apassenger's weight measurement device for a vehicle seat comprises anupper rail disposed to be movable back and forth on a lower rail fixedto a vehicle floor; a load sensor fixed on the upper rail; and a framedisposed on the load sensor and below a vehicle seat, wherein a rodextends from the load sensor to penetrate the frame and to be insertedinto an insertion hole formed in a center of a leaf spring, the leafspring is curved into an angle shape to separate the center of the leafspring from the frame, a nut is engaged with the rod on the leaf spring,and both hems of the leaf spring abut on the frame in a state that theleaf spring is fastened by the nut.

In accordance with a second aspect of the present invention, in anattachment structure for attaching a load sensor to a frame disposedbelow a vehicle seat, a rod extends from the load sensor to penetratethe frame and to be inserted into an insertion hole formed in a centerof a leaf spring, the leaf spring is curved into an angle shape toseparate the center of the leaf spring from the frame, a nut is engagedwith the rod on the leaf spring, and both hems of the leaf spring abuton the frame in a state that the leaf spring is fastened by the nut.

In accordance with the first and second aspects, preferably, a collarthrough which the rod is inserted penetrates the frame, the leaf springis held between the collar and the nut, and the leaf spring and thecollar are held between the nut and the load sensor.

In accordance with the first and second aspect, preferably, the rod isinserted into the insertion hole in a position shifted from a linesegment for interconnecting the both hems of the leaf spring when seentowards an inserting direction of the rod.

In accordance with the first and second aspects, preferably, holes areformed in the both hems of the leaf spring, and a part of a covercovering the both hems of the leaf spring is inserted into the holes.

According to the first and second aspects, because the leaf spring iscurved into an angle shape to separate the center of the leaf springfrom the frame, and the nut is engaged with the rod from above the leafspring, the frame is shifted in a vertical direction with respect to theload sensor. The fastening of the nut elastically deforms the leafspring.

According to the first and second aspects of the present invention, theframe is shifted in the vertical direction with respect to the loadsensor. Thus, even when the left and right lower rails, the left andright upper rails, the frame, or the like is distorted duringassembling, it is possible to avoid applying an initial load generatedby the distortion on the load sensor.

Because both hems of the leaf spring are in contact with the frame byfastening the nut, the load sensor is not loosened with respect to theframe. Thus, it is possible to suppress a reduction in rigidity.

Because the elastic deformation of the leaf spring by the nut applies aload on the nut from the leaf spring, it is possible to preventloosening of the nut.

In accordance with a third aspect of the present invention, apassenger's weight measurement device for a vehicle seat comprises apair of left and right upper rails disposed to be movable back and forthon a pair of left and right lower rails fixed to a vehicle floor; fourload sensors fixed on front and rear sides of the pair of upper rails;and a frame disposed on the four load sensors and below the vehicleseat, wherein two of the four load sensors, which are arranged on onediagonal line, are set to play in back-and-forth and left-and-rightdirections with respect to the frame, and the other two load sensorsarranged on the other diagonal line are fixed in back-and-forth andleft-and-right directions with respect to the frame.

According to the third aspect of the present invention, because the twoload sensors located on one diagonal line are set to play back and forthand left and right with respect to the frame, even when distortionoccurs in the upper rail or the lower rail, the load sensors located onone diagonal line are horizontally shifted with respect to the frame.Thus, no initial load generated by distortion is applied on the loadsensors.

In accordance with a fourth aspect of the present invention, apassenger's weight measurement device for a vehicle seat employs astructure in which a pair of side frames supporting the seat isstructured to be rigid, a pair of load cells located on one diagonalline among four load cells disposed between the seat and a vehicle floorare moveable up and down, and a pair of load cells located on the otherdiagonal line are moveable up and down and play.

More specifically, in accordance with the fourth aspect of the presentinvention, a passenger's weight measurement device for a vehicle seatcomprises a pair of slide rails arranged in a vehicle floor; a pair ofside frames for supporting the seat; and load cells disposed at fourcorners of the pair of slide rails and the pair of side frames, whereinthe pair of side frames constitute a rectangular seat frame with a setof first connection frames for connecting both ends the pair of sideframes extending in parallel so as to be perpendicular to the pair ofside frames.

According to the fourth aspect, the pair of side frames constitute arectangular seat frame with a set of first connection frames forconnecting both ends the pair of side frames extending in parallel so asto be perpendicular to the pair of side frames. Thus, the pair of siderails and the set of first connection frames are connected together,thereby providing a highly rigid rectangular seat frame.

The high rigidity of the seat frame may mean that distortion of the seatframe with respect to a force applied on the seat frame is small, forexample, displacement of the pair of side rails may be small withrespect to a force (compression stress) applied in a mutuallyapproaching direction of the pair of side rails, or displacement of thepair of side rails may be small with respect to a force (tension stress)applied in a mutually separating direction of the pair of side rails.According to the fourth aspect of the present invention, it is preventedthat an unnecessary force is applied on the load cell when the pair ofside frames slide together with the load cell on the slide rail. Then,it is possible to accurately measure passenger's load.

In accordance with the fourth aspect, preferably, in the pair of sliderails, a pair of first slide rails and a pair of second slide rails areconnected so as to be slidable, respectively, the pair of first sliderails extend in parallel to be fixed to the vehicle floor side, and thepair of first slide rails comprise a second connection frame forconnecting middle parts of the pair of first slide rails so as to beperpendicular to the first slide rails.

In this case, the pair of first slide rails and the second connectionframe are connected together to provide a highly rigid H-shaped frame(H-frame). The high rigidity of the H-frame may mean that distortion ofthe H-frame with respect to a force applied on the H-frame is small, forexample, displacement of the pair of first side rails may be small withrespect to a force (compression stress) applied in a mutuallyapproaching direction of the pair of first side rails, or displacementof the pair of first side rails may be small with respect to a force(tension stress) applied in a mutually separating direction of the pairof first side rails. According to the fourth aspect of the presentinvention, it is prevented that an unnecessary force is applied on theload cell. Then, it is possible to accurately measure passenger's load.

In accordance with the fourth aspect, preferably, the four load cellsare arranged at four corners of the pair of second slide rails, and thepair of second slide rails extend in parallel, and comprises a thirdconnection frame for connecting middle parts of the pair of second sliderails so as to be perpendicular to the second slide rails.

In this case, the pair of second slide rails and the third connectionframe are connected together to provide a highly rigid H-frame. The highrigidity of the H-frame may mean that distortion of the H-frame withrespect to a force applied on the H-frame is small, for example,displacement of the pair of second side rails may be small with respectto a force (compression stress) applied in a mutually approachingdirection of the pair of second side rails, or displacement of the pairof second side rails may be small with respect to a force (tensionstress) applied in a mutually separating direction of the pair of secondside rails. According to the fourth aspect of the present invention, itis prevented that an unnecessary force is applied on the load cell.Then, it is possible to accurately measure passenger's load.

In accordance with the fourth aspect, preferably, a pair of load cellslocated on one diagonal line among the four load cells are connected tobe movable up and down with respect to the seat frame, and a pair ofload cells located on the other diagonal line are connected to bemovable up and down and play with respect to the seat frame.

In this case, it is possible to absorb manufacturing errors of the pairof slide rails, the four load cells, and the pair of side frames, andheight-direction accumulated errors of these components. It is alsopossible to absorb assembling errors of the pair of slide rails, thefour load cells, and the pair of seat frames.

In accordance with the fourth aspect, preferably, in the set of firstconnection frames, one of the first connection frames is connected toends of the pair of side rails so as to be easily deformed by shockhaving a predetermined or more strength.

For example, in the pair of side frames, a pair of tongue pieces extendin one ends, and one of the first connection frames is connected to tipsof the pair of tongue pieces. Constrictions are disposed in base ends ofthe pair of tongue pieces, and shock stress concentrates on theseconstrictions. According to the fourth aspect of the present invention,by employing a structure easily deformed by shock having a predeterminedor more strength, it is possible to protect the load cells from shockhaving a predetermined or more strength.

In accordance with the fourth aspect, preferably, the load cellcomprises a male screw in one end and a flange in the other end locatedto face opposite to the one end, in the seat frame, four holes areformed to insert the male screws corresponding to an arrangement of thefour load cells, the pair of second slide rails are fixed to theflanges, first elastic bushes are inserted into a pair of first holeslocated on one diagonal line among the four holes, a first collar iselastically disposed between the first elastic bush and the male screw,a plain washer and a conical spring washer are mounted on the firstcollar, and a nut is fastened to the male screw, in a region of the seatframe, which is engaged with the pair of male screws located on the onediagonal line, an up-and-down moving amount is regulated by a length ofthe first collar in an axial direction, and the conical spring washerpresses the seat frame to the load cell side.

In this case, it is possible to realize a connection structure movableup and down by general mechanical elements. It is also possible toabsorb manufacturing errors of the pair of slide rails, the four loadcells and the seat frames, and height-direction accumulated errors ofthese components.

In accordance with the fourth aspect, preferably, second elastic bushesare inserted into a pair of second holes located on the other diagonalline among the four holes, a second collar is inserted after a plainwasher is inserted into the male screw, the second elastic bush isdisposed to play in the second collar, a conical spring washer aremounted on the second collar, and a nut is fastened to the male screw,in a region of the seat frame, which is engaged with the pair of malescrews located on the other diagonal line, an up-and-down moving amountis regulated by a length of the second collar in an axial direction, andthe conical spring washer presses the seat frame to the load cell side.

In this case, it is possible to realize a connection structure permittedto move up and down and to play by general mechanical elements. It isalso possible to absorb manufacturing errors of the pair of slide rails,the four load cells and the seat frames, and height-directionaccumulated errors of these components.

In accordance with the fourth aspect, preferably, an inner diameter ofthe first elastic bush is formed in a conical body, and an innerperiphery of an upper bottom surface of the conical body having a smallradius abuts on an outer periphery of the first collar.

In this case, it is possible to realize both of facilitation ofassembling and absorption of assembling errors by forming the innerdiameter of the first elastic bush in the conical body.

According to the fourth aspect of the present invention, the pair ofside frames supporting the seat and a set of first connection frames areconnected together to provide a highly rigid rectangular seat frame. Thepair of slide rails and the second and third connection frames areconnected together to provide a highly rigid H-frame. For example, it ispossible to prevent tilting of the load cell by moving the pair of sideframes in a mutually separating direction. According to the fourthaspect of the present invention, it is possible to provide a passenger'sweight measurement device for a vehicle seat, capable of preventinginterference with load cell load measurement without increasing thenumber of components and without greatly changing the framework of theconventional seat structure.

Furthermore, according to the fourth aspect of the present invention, itis possible to absorb manufacturing errors of the pair of slide rails,the four load cells and the seat frames, and height-directionaccumulated errors of these components. It is also possible to absorbhorizontal accumulated errors of the components caused by assembling.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinafter and the accompanying drawinggiven by way of illustration only, and thus are not intended as adefinition of the limits of the present invention, and wherein:

FIG. 1 is a perspective diagram showing a passenger's weight measurementdevice for a vehicle seat.

FIG. 2 is an exploded perspective diagram showing the passenger's weightmeasurement device.

FIG. 3 is a perspective diagram showing a load sensor.

FIG. 4 is a plan diagram showing a rectangular frame.

FIG. 5 is a plan diagram showing a right front section of therectangular frame.

FIG. 6 is a schematic sectional diagram cut along the line VI-VI of FIG.5.

FIG. 7 is a schematic sectional diagram cut along the line VII-VII ofFIG. 5.

FIG. 8 is a plan diagram showing a right rear section of the rectangularframe.

FIG. 9 is a schematic sectional diagram cut along the line IX-IX of FIG.8.

FIG. 10 is a schematic sectional diagram cut along the line X-X of FIG.8.

FIG. 11 is an exploded perspective assembly diagram showing apassenger's weight measurement device according to a second embodiment.

FIG. 12 is an exploded perspective diagram showing a seat sectionincluding the passenger's weight measurement device of the secondembodiment.

FIG. 13 is a perspective appearance diagram showing the passenger'sweight measurement device of the second embodiment.

FIG. 14 is a perspective appearance diagram showing a schematicconfiguration of the passenger's weight measurement device of the secondembodiment.

FIG. 15 is a perspective appearance diagram showing the passenger'sweight measurement device of the second embodiment.

FIG. 16 is an enlarged longitudinal sectional diagram of a main sectionof FIG. 15.

FIG. 17 is an enlarged plan diagram of a main section of FIG. 16.

FIG. 18 is a longitudinal sectional diagram showing the first elasticbush applied to the passenger's weight measurement device of the secondembodiment.

FIG. 19 is a longitudinal sectional diagram of a load cell located onone diagonal line in the passenger's weight measurement device of thesecond embodiment.

FIG. 20 is a longitudinal sectional diagram of a load cell located onthe other diagonal line in the passenger's weight measurement device ofthe second embodiment.

PREFERRED EMBODIMENT OF THE INVENTION

The preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings. In the embodimentsdescribed below, various preferable technical limitations are describedto carry out the invention, but the scope of the invention is notlimited to the embodiment and the examples shown in the figures.

(First Embodiment)

FIG. 1 is a perspective diagram of a passenger's weight measurementdevice 1 for a vehicle seat, and FIG. 2 is an exploded perspectivediagram of the passenger's weight measurement device 1.

As shown in FIGS. 1 and 2, a slide adjuster 2 for adjusting aback-and-forth position of the vehicle seat is mounted to a floor of apassenger's room. The slide adjuster 2 includes lower rails 3 and 4disposed in parallel with each other, an upper rail 5 engaged with thelower rail 3 to slide back and forth on the lower rail 3 with respect tothe same, an upper rail 6 engaged with the lower rail 4 to slide backand forth on the lower rail 3 with respect to the lower rail 4, a lowerbracket 7 fixed to bottom surfaces of the lower rails 3 and 4 by boltsand nuts or rivets to bridge a gap therebetween, a lock mechanism 8 forlocking/unlocking the upper rails 5 and 6 to/from the lower rails 3 and4, brackets 31 and 33 fixed to the bottom surface of the lower rail 3,and brackets 32 and 34 fixed to the bottom surface of the lower rail 4.The brackets 31 to 34 are mounted to the vehicle floor, and the lowerrails 3 and 4 are fixed to the vehicle floor.

A bracket 11 is fixed to a back-and-forth direction center of an uppersurface of the right upper rail 5 by bolts and nuts or rivets, and abracket 12 is fixed to a back-and-forth direction center of an uppersurface of the left upper rail 6 by bolts and nuts or rivets. Bothbrackets 11 and 12 are disposed to be upright on the upper surfaces ofthe upper rails 5 and 6. A right end of a submarine pipe 10 is welded tothe bracket 11, and a left end of the submarine pipe 10 is welded to thebracket 12, thereby installing the submarine pipe 10 between thebrackets 11 and 12.

A load sensor 21 is mounted on a front end of the upper surface of theright upper rail 5, and a load sensor 23 is mounted on a rear end of theupper surface of the right upper rail 5. Similarly, a load sensor 22 ismounted on a front end of the upper surface of the left upper rail 6,and a load sensor 24 is mounted on its rear end. Seen from the above,the load sensors 21 to 24 are arranged to be apexes of a square or arectangle.

FIG. 3 is a perspective diagram of the load sensor 21. As shown in FIG.3, the load sensor 21 includes a columnar sensing section 21 a fordetecting a load, a platelike flange section 21 b extending laterallyback and forth from a lower end of the sensing section 21 a, a rod 21 cextending from an upper end of the sensing section 21 a upward, and aconnector 21 d extending from the sensing section 21 a to be parallel tothe flange section 21 b. The rod 21 c is formed into a male screw shape.Female screw-shaped circular holes 21 e and 21 f put-through up and downare formed in front and rear parts of the flange section 21 b. Thesensing section 21 a incorporates a strain gauge for converting a loadinto an electric signal.

As shown in FIG. 2, the load sensor 21 is secured to the right upperrail 5. Specifically, a bottom surface of the flange section 21 b abutson the upper surface of the upper rail 5, and bolts 35 and 36penetrating the upper rail 5 up and down are engaged with the circularholes 21 e and 21 f to fix the load sensor 21. The load sensor 21 may befixed to the upper rail 5 by fastening nuts around the bolts 35 and 36on the flange section 21 b without forming any screw threads in thecircular holes 21 e and 21 f.

The load sensors 22 to 24 are all configured as in the case of the loadsensor 21. Thus, the load sensors 22 to 24 will be described by usingreference numerals of sensing section 22 a to 24 a, flange sections 22 bto 24 b, rods 22 c to 24 c, and connector 22 d to 24 d.

As in the case of the load sensor 21, the load sensor 23 is fixed to theupper surface of the right upper rail 5 by a bolt 37, and the loadsensors 22 and 24 are fixed to the upper surface of the left upper rail6 by bolts 38 and 39.

In the fixed state of the load sensors 21 to 24, the connectors 23 d and24 d are directed forward for the rear load sensors 23 and 24, and theconnectors 21 d and 22 d are directed backward for the front loadsensors 21 and 22.

As shown in FIGS. 1 and 2, rectangular frames 40 are mounted on the loadsensors 21 to 24. FIG. 4 is a top diagram of the rectangular frame 40.As shown in FIG. 4, the rectangular frame 40 includes a right beam 41, aleft beam 42, a front member 43, and a rear cross pipe 44.

The right beam 41 is a metal material having a web 41 a and left andright flanges 41 b and 41 c and U-shaped in section. A length infront-and-rear direction of the web 41 a is longer than those of theflanges 41 b and 41 c, and a front end 41 d of the web 41 a extendsbefore front ends of the flanges 41 b and 41 c. A rectangular notch 41 eis formed in a side edge of the front end 41 d of the web 41 a, and awidth of this part is narrower than those of other parts. A mountinghole 41 f is formed in a front of the web 41 a, and a mounting hole 41 gis formed in a rear part of the web 41 a. The mounting hole 41 f islocated behind the notch 41 e. A diameter of the rear mounting hole 41 gis larger than that of the front mounting hole 41 f.

Similarly, the left beam 42 is a metal material having a web 42 a andleft and right flanges 42 b and 42 c and U-shaped in section, and anotch 42 e is formed in a side edge of a front end 42 d of the web 42 a.Mounting holes 42 f and 42 g are formed in the web 42 a, back-and-forthpositions of the mounting holes 42 f and 41 f are almost aligned witheach other, back-and-forth positions of the mounting holes 42 g and 41 gare almost aligned with each other, and the attaching hole 42 f islocated behind the notch 42 e. In the left beam 42, a diameter of thefront mounting hole 42 f is larger than that of the rear mounting hole42 g.

The front member 43 is a metal member having a web and a flange andU-shaped in section. A right end of the front member 43 is welded to thefront end 41 d of the web 41 a on a front side of the notch 41 e of thebeam 41, and a left end of the front member 43 is welded to the frontend 42 d of the web 42 a on a front side of the notch 42 e of the beam42.

The cross pipe 44 is installed between the rear ends of the beams 41 and42 to be welded to the same. As in the case of the front notches 41 eand 42 e, a notch may be formed in the beam 41 between the cross pipe 44and the load sensor 23, or in the beam 42 between the cross pipe 44 andthe load sensor 24.

Referring to FIGS.5 to 7, a structure for mounting the right front loadsensor 21 to the rectangular frame 40 will be described. FIG. 5 is aplan diagram of a right front part of the rectangular frame 40, FIG. 6is a schematic sectional diagram cut along the line VI-VI, and FIG. 7 isa schematic sectional diagram cut along the line VII-VII. As shown inFIGS.5 to 7, a ring-shaped nylon bush 61 is fitted in an edge of theright front mounting hole 41 f, and grease is applied on the nylon bush61. A stepped collar 62 constituted of a cylindrical part 62 a and aring platelike flange part 62 b formed in one end surface of thecylindrical part 62 a is inserted into the mounting hole 41 f inside thenylon bush 61. In this case, the cylindrical part 62 a penetrates theweb 41 a from bottom up, and the flange part 62 b engages the bottomsurface of the web 41 a, thereby preventing pulling-out of the steppedcollar 62 upward. The cylindrical part 62 a projects more than the uppersurface of the web 41 a, and an upper end surface of the cylindricalpart 62 a is located higher than the upper surface of the web 41 a. Thecylindrical part 62 a is fitted to the nylon bush 61 to leave no spacebetween the cylindrical part 62 a and the nylon bush 61.

The rod 21 c of the load sensor 21 is inserted into the stepped collar62, and this rod 21 c penetrates the web 41 a from bottom up. An innerdiameter of the stepped collar 62 is designed to be slightly larger thana diameter of the rod 21 c. By such designing, a dimension error and amounting position error are prevented. Accordingly, even when thediameter of the rod 21 c is smaller than the inner diameter of thestepped collar 62, the rod 21 c is fixed to the beam 41 withsubstantially no play in back-and-forth and left-and-right directions.

A nut 66 is engaged with the rod 21 c, a plain washer 63 and a leafspring 64 are disposed between the upper surface of the web 41 a of thebeam 41 and the nut 66, and the nut 66 is engaged with the leaf spring64. The rod 21 c is inserted into the plain washer 63, and the plainwasher 63 is mounted on an end surface of the stepped collar 62. Theplain washer 63 is located apart from the upper surface of the web 41 aof the beam 41.

The leaf spring 64 is formed into an isosceles triangular shape, aninsertion hole is formed in its center (center of gravity of theisosceles triangle), and the rod 21 c is inserted into this insertionhole. Corners of the leaf spring 64 equal to each other are covered withcovers 65, and grease is applied on the covers 65. The cover 65 isformed by molding and hardening a fluid resin at the corner of the leafspring 64, and a part of the cover 65 is inserted into a hole 64 aformed at the corner of the leaf spring 64. Seen from the side, the leafspring 64 is curved so that a center of the leaf spring 64 can beangled, and the corner covered with the cover 65 is hemmed. By fasteningthe nut 66, the plain washer 63 and the leaf spring 64 are held betweenthe nut 66 and the upper end surface of the cylindrical part 62 a, andthe leaf spring 64, the plain washer 63 and the stepped collar 62 a areheld between the nut 66 and the load sensor 21. By fastening the nut 66,the covers 65 of both hems of the leaf spring 64 abut on the uppersurface of the web 41 a of the beam 41 to press the leaf spring 64 tothe web 41 a. The insertion hole into which the rod 21 c has beeninserted is formed in the center-of-gravity part of the leaf spring 64.Accordingly, seen from the insertion direction of the rod 21 c, the rod21 c is inserted into the insertion hole in a position shifted from aline for interconnecting both corners of the leaf spring which becomes acontact between the leaf spring 64 and the web 41 a.

Since the fastening of the nut 66 causes elastic deformation of the leafspring 64, a load is applied on the nut 66 to prevent its loosening. Asthe rod 21 c is inserted into the stepped collar 62, even when the nut66 is excessively fastened, it is possible to prevent bonding of theentire leaf spring 64 to the upper surface of the web 41 a caused byflat deformation of the leaf spring 64.

A position of the mounting hole 41 f in a width direction of the web 41a is slightly right from a center, and both hems of the leaf spring 64are in contact with a width-direction center of the web 41 a.

Referring to FIGS.8 to 10, a structure for mounting the right rear loadsensor 23 to the rectangular frame 40 will be described. FIG. 8 is aplan diagram of a right rear part of the rectangular frame 40, FIG. 9 isa schematic sectional diagram cut along the line IX-IX, and FIG. 10 is aschematic sectional diagram cut along the line X-X.

As shown in FIGS.8 to 10, a ring-shaped nylon bush 71 is fitted in anedge of the right rear mounting hole 41 g, and grease is applied on thenylon bush 71. The rod 23 c of the load sensor 23 is inserted into aplain washer 73, and inserted into the mounting hole 41 g to penetratethe web 41 a from bottom up. The plain washer 73 is held between the web41 a of the beam 41 and the sensor part 23 a.

The rod 23 c is inserted into the cylindrical part 72 a of a steppedcollar 72, the cylindrical part 72 a penetrates the web 41 a from bottomup inside the nylon bush 71, and a lower end surface of the cylindricalpart 72 a abuts on the plain washer 73. A ring-shaped flange part 72 bis formed in an upper end surface of the cylindrical part 72 a, and thisflange part 72 b is above the web 41 a. The flange part 72 b and the web41 a are apart from each other. An inner diameter of the stepped collar62 is almost equal to a diameter of the rod 23 c, and an outer diameterof the cylindrical part 72 a is slightly smaller than a diameter of themounting hole 41 g. Thus, there is a space between an outer peripheralsurface of the cylindrical part 72 a and the edge of the mounting hole41 g, and the rod 23 c is set with a play back and forth and left andright with respect to the beam 41.

A nut 76 is engaged with the rod 23 c, a leaf spring 74 is disposedbetween the flange part 72 b of the stepped collar 72 and the nut 76,and the nut 76 is engaged with the leaf spring 74. The leaf spring 74 isformed into an isosceles triangular shape, an insertion hole is formedin its center (center of gravity of the isosceles triangle), and the rod23 c is inserted into this insertion hole. Corners of the leaf spring 74equal to each other are covered with covers 75, and grease is applied onthe covers 75. The cover 75 is formed by molding and hardening a fluidresin at the corner of the leaf spring 74, and a part of the cover 75 isinserted into a hole 74 a formed at the corner of the leaf spring 74.Seen from the side, the leaf spring 74 is curved so that a center of theleaf spring 74 can be angled, and the corner covered with the cover 75is hemmed. By fastening the nut 76, the leaf spring 74 is held betweenthe nut 76 and the stepped collar 72, the leaf spring 74, the steppedcollar 72 and the plain washer 73 are held between the nut 76 and theload sensor 23. By fastening the nut 76, the covers 75 of both hems ofthe leaf spring 74 abut on the upper surface of the web 41 a of the beam41 to press the leaf spring 74 to the web 41 a. Since the fastening ofthe nut 76 causes elastic deformation of the leaf spring 74, a load isapplied on the nut 76 to prevent its loosening. As the rod 23 c isinserted into the stepped collar 72, even when the nut 76 is excessivelyfastened, it is possible to prevent bonding of the entire leaf spring 74to the upper surface of the web 41 a caused by flat deformation of theleaf spring 74.

As the insertion hole inserted into the rod 23 c is formed in thecenter-of-gravity of the leaf spring 74, seen to the insertion directionof the rod 23 c, the rod 23 c is inserted into the insertion hole in aposition shifted from a line for interconnecting both hem corners of theleaf spring 74 which becomes a contact between the leaf spring 74 andthe web 41 a. A position of the mounting hole 41 g in the widthdirection of the web 41 a is slightly right from the center, and bothhems of the leaf spring 74 are in contact with the width-directioncenter of the web 41 a.

As shown in FIG. 2, a mounting structure of the left front load sensor22 to the mounting hole 42 f is similar to that of the right rear loadsensor 23 to the mounting hole 41 g, and a mounting structure of theleft rear load sensor 24 to the mounting hole 42 g is similar to that ofthe right front load sensor 21 to the mounting hole 41 f. In otherwords, the load sensors 21 and 24 at opposite corners are fixed to therectangular frame 40 without any play in a back-and-forth orleft-and-right direction, while the load sensors 23 and 22 at otheropposing corners are fixed to the rectangular frame 40 with play inback-and-form and left-and-right directions by an amount equal to aspace between the outer peripheral surface of the cylindrical part 72 aand the mounting hole 41 g.

In the state in which the rectangular frame 40 is mounted on the loadsensors 21 to 24 as described above, the submarine pipe 10 is located ona side behind the front member 43.

As shown in FIGS. 1 to 2, a side frame 51 is welded to the right flange41 b of the beam 41, and a side frame 52 is welded to the left flange 42b of the beam 42. These side frames 51 and 52 are parts of a bottomframe of the vehicle seat.

Front parts of the side frames 51 and 52 are covered with a pan frame 53from the above, and the side frames 51 and 52 are connected to the panframe 53 by bolts and nuts or rivets. A sheet spring 54 is installedbetween a cross pipe 44 and the pan frame 53, a cushion is mounted onthe pan frame 53 and the sheet spring 54, and the cushion, the pan frame53 and the side frames 51 and 52 are entirely covered with a cover.

A backrest frame is connected to rear ends of the side frames 51 and 52to rise and fall by a reclining mechanism. The backrest frame and thecushion are not shown for easier viewing of the drawings.

When the passenger's weight measurement device 1 is assembled, thebrackets 11 and 12 and the submarine pipe 10 are fitted to the assembledslide adjuster 2, the load sensors 21 and 23 are fitted to the uppersurface of the right upper rail 5, and the load sensors 22 and 24 arefitted to the upper surface of the left upper rail 6. Then, therectangular frame 40 is fitted to the load sensors 21 to 24 by using thenylon bushes 61 and 71, the stepped collars 62 and 72, the plain washers63 and 73, the leaf springs 64 and 74, and the nuts 66 and 76. When therectangular frame 40 is fitted, even when positions of the load sensors21, 23, 22 and 24 are not aligned with those of the mounting holes 41 f,41 g, 42 f and 42 g as designed, errors can be eliminated as thediameters of the rods 21 c and 24 c are smaller than the inner diameterof the stepped collar 62 in the right front and left rear load sensors21 and 24.

When the assembled passenger's weight measurement device 1 is fitted toa vehicle, the brackets 31 to 34 of the slide adjuster 2 are mounted toa floor in the vehicle by bolts and nuts or rivets. If positions ofmounting parts of the brackets 31 to 34 are not aligned with designedpositions of the brackets 31 to 34, when the brackets 31 to 34 aremounted to the floor, the slide adjuster 2 or the like is slightlydistorted. However, as the right rear load sensor 23 and the left frontload sensor 22 are set to play in the back-and-forth and left-and-rightdirections of the rectangular form 40, even when the slide adjuster 2 orthe like is distorted, the load sensors 22 and 23 are horizontallyshifted from the rectangular frame 40 to prevent application of aninitial load on the load sensors 21 to 24 caused by distortion.Moreover, as the rectangular frame 40 is shifted vertically with respectto the load sensors 21 to 24 by the stepped collars 62 and 72,application of an initial load on the load sensors 21 to 24 caused bydistortion of the slide adjuster 2 or the like is prevented. Even whenthe load sensors 21 to 24 are shifted with respect to the rectangularframe 40, as the leaf springs 64 and 74 are present between the nuts 66and 76 and the webs 41 a and 42 a, the load sensors 21 to 24 are notloosened with respect to the rectangular frame 40 thereby causing norigidity problem.

According to the passenger's weight measurement device 1 configured asdescribed above, when a passenger sits on the seat bottom, a weight ofthe passenger is applied through the rectangular frame 40 on the loadsensors 21 to 24, and converted into an electric signal by the loadsensors 21 to 24.

Because of the configuration in which the right load sensors 21 and 23are mounted between the upper rail 5 and the rectangular frame 40, theleft load sensors 22 and 24 are mounted between the upper rail 6 and therectangular frame 40, and the load sensors 21 to 24 move back and forthintegrally with the vehicle seat, irrespective of the back-and-forthposition of the vehicle seat, a load input from the vehicle seat to theload sensors 21 to 24 can always be maintained constant. Accordingly, itis possible to improve measuring accuracy of passenger's weight.

As the submarine pipe 10 is located behind the front member 43, whenfront collision or the like of the vehicle applies a forward inertialforce on the passenger, a buttocks of the passenger sitting on thevehicle seat is held by the submarine pipe 10. Thus, it is possible toprevent a so-called submarine phenomenon in which the passenger getsunder a waist belt.

As the submarine pipe 10 is disposed separately from the front member43, the buttocks of the passenger do not come into contact with thefront member 43 at the time of front collision or the like of thevehicle. Accordingly, the forward inertial force at the time of frontcollision or the like of the vehicle is prevented from being transmittedthrough the rectangular frame 40 to the load sensors 21 to 24. Thus,even at the time of front collision or the like of the vehicle, it ispossible to improve measuring accuracy of the passenger's weight.

None of the flanges 41 b, 41 c, 42 b and 42 c are disposed in the frontend of the beams 41 and 42, only the webs 41 a and 42 a are present. Thenotches 41 e and 42 e are formed in the front ends 41 d and 42 d of thewebs 41 a and 42 a, and the front member 43 is mounted in front of thenotches 41 e and 42 d. Accordingly, when a large load is applied on therectangular frame 40 at the time of front collision or the like of thevehicle, the beams 41 and 42 are deformed at the notches 41 e and 42 d,whereby the load is reduced at the deformed places. Hence, even when thelarge load is applied on the rectangular frame 40, transmission of thelarge load to the load sensors 21 to 24 is prevented. Thus, even at thetime of front collision or the like of the vehicle, it is possible toimprove measuring accuracy of the passenger's weight and to suppressdamaging of the load sensors 21 to 24.

(Second Embodiment)

FIG. 11 is an exploded perspective assembly diagram showing apassenger's weight measurement device according to a second embodiment.FIG. 12 is an exploded perspective assembly diagram of a seat sectionincluding the passenger's weight measurement device of the secondembodiment. FIG. 13 is a perspective appearance diagram showing thepassenger's weight measurement device of the second embodiment. FIG. 14is a perspective appearance diagram showing a schematic configuration ofthe passenger's weight measurement device of the second embodiment. FIG.15 is a perspective appearance diagram showing the passenger's weightmeasurement device of the second embodiment. FIG. 16 is a longitudinalsectional diagram of an enlarged main section of FIG. 15. FIG. 17 is aplan diagram of an enlarged main section of FIG. 16.

FIG. 18 is a longitudinal sectional diagram of a first elastic bushapplied to the passenger's weight measurement device of the secondembodiment. FIG. 19 is a longitudinal sectional diagram of a load celllocated on one diagonal line in the passenger's weight measurementdevice of the second embodiment. FIG. 20 is a longitudinal sectionaldiagram of a load cell located on the other diagonal line in thepassenger's weight measurement device of the second embodiment.

Referring to FIGS. 11 and 12, a pair of slide rails 2 a and 2 b arearranged in a vehicle floor. A seat includes a seat 40 and a backrest50, and the seat 40 is supported by a pair of side frames 3 a and 3 b.Load cells 1 are disposed at four corners of the pair of slide rails 2 aand 2 b and the pair of side frames 3 a and 3 b. A seat frame 30includes a pair of side frames 3 a and 3 b extending in parallel, and aset of first connection frames 3 c and 3 d for connecting both ends ofthe pair of side frames 3 a and 3 b to be perpendicular to the sideframes 3 a and 3 b. In the pair of slide rails 2 a and 2 b, a pair offirst slide rails 21 a and 21 b and a pair of second slide rails 22 aand 22 b are connected to slidable, respectively.

The passenger's weight measurement device is usually disposed in apassenger seat of a vehicle to detect a weight of a passenger of theseat. An airbag system mounted on the passenger seat is controlledcorresponding to a detection signal obtained by the passenger's weightmeasurement device. It is possible to estimate the weight of thepassenger of the seat via the passenger's weight measurement deviceprovided between the seat 40 and the vehicle floor. In FIG. 12, cushionsof the seat 40 and the backrest 50 are omitted.

Referring to FIGS. 11 and 12, the pair of side frames 3 a and 3 b are Cchannel members in which both wings are bent. Such a C channel membercan effectively enlarge sectional secondary moment by contriving theshapes without increasing weight, and rigidity to a bending force can beimproved. The pair of side frames 3 a and 3 b are arranged in thevehicle with bent pieces of both wings set upward.

Referring to FIGS. 11 and 12, the first connection frame 3 c of the setof first connection frames 3 c and 3 d is made of a C channel member inwhich both wings are bent. Both ends of the first connection frame 3 care connected to one end of the pair of the side frames 3 a and 3 b. Thepair of side frames 3 a and 3 b and the first connection frame 3 c areconnected together by fasteners such as screws. The first connectionframe 3 d of the set of first connection frames 3 c and 3 d is a roundpipe. Both ends of this round pipe are connected to the other ends ofthe pair of side frames 3 a and 3 b.

Referring to FIGS. 11 and 12, the pair of first slide rails 21 a and 21b extend in parallel to be fixed to the vehicle floor side. The pair offirst slide rails 21 a and 21 d include a second connection frame 21 cfor connecting middle parts of the pair of first slide rails 21 a and 21b to be perpendicular to the first slide rails 21 a and 21 b. The pairof first slide rails 21 a and 21 b each includes a slide locking devicenot shown in the drawings, and a lever 23 is connected to operate theslide locking device. The seat 40 can be slid by gripping the lever 23.The pair of second slide rails 22 a and 22 b extend in parallel andinclude a third connection frame 22 c for connecting middle parts of thepair of second slide rails 22 a and 22 b to be perpendicular to thesecond slide rails 22 a and 22 b.

Referring to FIGS. 11 and 12, both ends of the pair of first slide rails21 a and 21 b are fixed to the vehicle floor via a pair of supportbrackets 24 and 25. The second connection frame 21 c is a wide C channelmember, and both ends of the second connection frame 21 c are connectedto the middle parts of the pair of first slide rails 21 a and 21 b.

Referring to FIGS. 11 and 12, the third connection frame 22 c includes around pipe 220 and a pair of angle members 221 and 222, and the anglemembers 221 and 222 are connected to both ends of the round pipe 220 sothat pieces thereof can face each other. For example, the angle members221 and 222 and the round pipe 220 may be bonded together by welding, orcaulking. The other pieces of the angle members 221 and 222 areconnected to the middle parts of the pair of second slide rails 22 a and22 b. Both ends of the third connection frame 22 c are connected to themiddle parts of the pair of second slide rails 22 a and 22 b byfasteners such as screws.

Referring to FIG. 14, the pair of side frames 3 a and 3 b and the set offirst connection frames 3 c and 3 d are connected together so that ahighly rigid rectangular frame seat frame 30 can be obtained. The seatframe 30 holds the seat 40 (FIG. 12). In this case, high rigidity of theseat frame 30 may mean that distortion of the seat frame 30 is smallwith respect to a force applied on the seat frame 30, for example,displacement of the pair of side frames 3 a and 3 b is small withrespect to a force (compression stress) applied in a mutuallyapproaching direction of the pair of side frames 3 a and 3 b, ordisplacement of the pair of side frames 3 a and 3 b is small withrespect to a force (tension stress) applied in a mutually separatingdirection of the pair of side frames 3 a and 3 b.

Referring to FIG. 14, the pair of first slide rails 21 a and 21 b andthe second connection frame 21 c are connected together to obtain ahighly rigid H-shaped frame (H-frame). The pair of second slide rails 22a and 22 b and the third connection frame 22 c are connected together toobtain a highly rigid H-frame. The high rigidity of the H-frame may meanthat distortion of the H-frame is small with respect to a force appliedon the H-frame, for example, displacement of the pair of slide rails 2 aand 2 b is small with respect to a force (compression stress) applied ina mutually approaching direction of the pair of slide rails 2 a and 2 b,or displacement of the pair-of slide rails 2 a and 2 b is small withrespect to a force (tension stress) applied in a mutually separatingdirection of the pair of slide rails 2 a and 2 b (FIGS. 11 and 12).

Referring to FIGS. 11 and 12, in the passenger's weight measurementdevice, four load cells 1 are arranged at four corners of the pair ofsecond slide rails 22 a and 22 b. The four load cells 1 connect the seatframe 30 to the pair of second slide rails 22 a and 22 b.

Referring to FIGS. 11 and 12, a weight of a passenger of the seat 40 canbe estimated by summing up detection values of the four load cells 1.The load cell 1 includes a male screw 1 a in one end, and a flange 1 bin the other end located to face one end. The male screw 1 a isconnected to the seat frame 30. The connection means a connection toenable up-and-down movement in an axial direction, or a connection toenable up-and-down movement in axial and circumferential directions. Theflange 1 b is connected to the pair of second slide rails 22 a and 22 b.The flange 1 b is connected to the pair of second slide rails 22 a and22 b by a fastener constituted of a hexagon socket bolt 1 h and a nut 1j (FIG. 19).

According to the passenger's weight measurement device of the presentinvention, the pair of side frames 3 a and 3 b supporting the seat andthe set of the first connection frames 3 c and 3 d are interconnected toobtain the highly rigid rectangular frame seat frame 30. The pair ofslide rails 21 a and 21 b and the second connection frame 21 c areinterconnected to obtain the highly rigid H-frame, and the pair of sliderails 22 a and 22 b and the third connection frame 22 c areinterconnected to obtain the highly rigid H-frame. For example, the pairof side frames 3 a and 3 b move in a mutually separating direction toenable prevention of tilting of the load cells 1. According to thepresent invention, it is possible to provide the passenger's weightmeasurement device capable of preventing interferences with loadmeasurement of the load cells without increasing the number ofcomponents and without greatly changing the framework of theconventional seat structure.

Referring to FIG. 13, in the passenger's weight measurement device ofthe present invention, among the four load cells 1 aa, 1 ab, 1 ba and 1bb, the pair of load cells 1 aa and 1 bb located on one diagonal lineare connected to the seat frame 30 to be movable up and down. The pairof load cells 1 ab and 1 ba located on the other diagonal line areconnected to the seat frame 30 to be movable up and down and play. Fourload cells, 1 aa, 1 ab, 1 ba, and 1 bb shown in FIG. 13 are the same asthe load cells 1 shown in FIGS. 11 and 12, but they are denoted byreference numerals to be differentiated for convenience of explanation.

As described above, the load cell 1 includes the male screw 1 a in oneend, and the flange 1 b in the other end located to face one end (FIG.14). In FIG. 13, the connection of the pair of load cells 1 aa and 1 bbto the seat frame 30 to be movable up and down is equivalent toconnection of the pair of male screws 1 a and 1 a to the seat frame 30to move up and down. The connection of the pair of load cells 1 ab and 1ba to the seat frame 30 to move up and down and play is equivalent toconnection of the pair of male screws 1 a and 1 a to the seat frame 30to be movable and play up and down.

The passenger's weight measurement device of the present invention canabsorb manufacturing errors of the pair of slide rails 22 a and 22 b,the four load cells 1, and the pair of side frames 3 a and 3 b, andheight-direction accumulated errors of these components. The device canalso absorb assembling errors of the pair of slide rails 22 a and 22 b,the four load cells 1 and the seat frame 30. The up-and-down movableconnection structure and the up-and-down movable and playable connectionstructure should preferably be realized by general mechanical elementssuch as bushes or washers without using any special mechanical elements.A specific embodiment will be described below.

According to the passenger's weight measurement device of the presentinvention, among the set of first connection frames 3 c and 3 d, thefirst connection frame 3 c is connected to one end of the pair of sideframes 3 a and 3 b to be easily deformed by shocks having apredetermined or more strength (FIG. 15).

Referring to FIG. 15, in the pair of side frames 3 a and 3 b, a pair oftongue pieces 33 a and 33 b extend to one end. The first connectionframe 3 c is connected to tips of the pair of tongue pieces 33 a and 33b. Constricted parts 34 a and 34 b are disposed in base ends of the pairof tongue pieces 33 a and 33 b (FIG. 17). Stress due to shocksconcentrates on the pair of constricted parts 34 a and 34 b.Accordingly, it is possible to protect the load cells from shocks havinga predetermined or more strength by employing the structure to be easilydeformed by shocks having a predetermined or more strength.

As shown in FIG. 16, the pair of cushion frames constituting the seat 40are connected to the round pipe 220. However, according to thepassenger's weight measurement device of the present invention, the pairof second slide rails 22 a and 22 b are connected together by the roundpipe 220 (FIG. 11). Thus, by changing the fixation of the round pipe 220for receiving a load of the passenger during collision from the pair ofcushion frames to the pair of second slide rails 22 a and 22 b, it ispossible to protect the load cells from shocks having a predetermined ormore strength.

Next, a load cell mounting structure of the passenger's weightmeasurement device of the present invention will be described.

Referring to FIG. 14, the load cell 1 includes the male screw 1 a in oneend. The load cell 1 includes the flange 1 b in the other end located toface one end. In the seat frame 30, four holes 3 aa, 3 ab, 3 ba and 3 bbfor entering male screws are formed corresponding to the arrangement ofthe four load cells 1. The pair of second slide rails 22 a and 22 b fixthe flanges 1 b.

Referring to FIGS. 14 and 19, first elastic bushes 31 b are insertedinto the pair of first holes 3 aa and 3 bb located on one diagonal line.A first collar 31 k is elastically provided between the first elasticbush 31 b and the male screw 1 a. A plain washer 1 w and a conicalspring washer 1 s are mounted on the first collar 31 k, and a nut in isconnected to the male screw 1 a.

For example, the first elastic bush is made of a synthetic resin such asnylon (registered trademark). The bush is a ring-shaped member, andcalled a grommet. The bush includes a groove in an outer peripheraldirection, and this groove is engaged with peripheral edges of the firstholes 3 aa and 3 bb. For example, the insertion of the first elasticbushes 31 b into the pair of first holes 3 aa and 3 bb may bepress-insertion of the first elastic bushes into the first holes 3 aaand 3 bb. An inner periphery of the first elastic bush 31 b elasticallyabuts on an outer periphery of the first collar 31 k (FIG. 19).

Referring to FIG. 19, in a portion of the seat frame 30, which isengaged with the pair of male screws located on one diagonal line, theup-and-down moving amount thereof is defined by an axial-directionlength of the first collar 31 k. The conical spring washer 1 s pressesthe seat frame 30 to the load cell 1 side.

Referring to FIG. 19, the first collar 31 k includes a circular flangein on end. The first collar 31 k is inserted into the male screw 1 afrom this flange. Then, the first collar 31 k is inserted into the firsthole 3 aa and 3 bb equipped with the first elastic bushes 31 b. At thistime, one surface of the first elastic bush 31 b abuts on the flange ofthe first collar 31 k. The plain washer 1 w is inserted into the malescrew 1 a. At this time, for example, the other surface of the firstelastic bush 31 b is separated from the plain washer 1 w while the plainwasher 1 w abuts on the other end of the first collar 31 k.Subsequently, the conical spring washer 1 s is mounted, and the nut 1 nis connected to the male screw 1 a. The nut in is preferably a preberingtorque nut.

According to the passenger's weight measurement device of the presentinvention, it is possible to realize the up-and-down movable structureby general mechanical elements without using any special mechanicalelements. Besides, it is possible to absorb manufacturing errors of thepair of slide rails 22 a and 22 b, the four load cells 1, and the pairof side frames 3 a and 3 b, and height-direction accumulated errors ofthese components.

Referring to FIGS. 14 and 20, the second elastic bush 32 b is insertedinto the pair of second holes 3 ab and 3 ba located on the otherdiagonal line. The second elastic bush 32 b includes a groove disposedin an outer peripheral direction, and this groove is engaged withperipheral edges of the second holes 3 ab and 3 ba. For example, theinsertion of the second elastic bushes 32 b into the pair of secondholes 3 ab and 3 ba may be press-insertion of the second elastic bushes32 b into the second holes 3 ab and 3 ba. In FIG. 20, an inner diameterof the second elastic bush 32 b is larger than an outer diameter of thesecond collar 32 k, and the second elastic bush 32 b holds the secondcollar 32 k to play. The play may be movement with play, and it ispossible to absorb manufacturing errors of the pair of slide rails 22 aand 22 b, the four load cells 1 and the pair of side frames 3 a and 3 b,and horizontal assembling errors of these components.

Referring to FIGS. 14 and 20, the plain washer 1 w is first insertedinto the male screw part 1 a. Then, the second holes 3 ab and 3 baequipped with the second elastic bushes 32 b are inserted into the malescrews 1 a. The second collar 32 k includes a circular flange in oneend. The second collar 32 k is inserted into the male screw 1 a withthis flange as a tail end. At this time, for example, an outer peripheryof the second collar 32 k is separated from an inner periphery of thesecond elastic bush 32 b. The conical spring washer 1 s is mounted, andthe nut 1 n is connected to the male screw 1 a. For example, the firstand second elastic bushes 31 b and 32 b may be identical, and used bychanging an insertion order and direction into the male screws 1 a.

According to the passenger's weight measurement device of the presentinvention, it is possible to realize the up-and-down movable andplayable structure by general mechanical elements without using anyspecial mechanical elements. Moreover, it is possible to absorbmanufacturing errors of the pair of slide rails 22 a and 22 b, the fourload cells 1, and the pair of side frames 3 a and 3 b, andheight-direction accumulated errors of these components.

Referring to FIG. 18, the inner diameter of the first elastic bush 31 bis formed into a conical shape, and an inner periphery of an upperbottom surface of the conical form of a small radius abuts on the outerperiphery of the first collar 31 k (FIG. 19). Thus, it is possible tosimultaneously achieve assembling easiness and assembling errorabsorption by forming the inner diameter of the first elastic bush 31 binto the conical shape.

According to the passenger's weight measurement device of the presentinvention, the pair of side frames 3 a and 3 b supporting the seat areconnected to the set of first connection frames 3 c and 3 d to obtain ahighly rigid rectangular frame seat frame 30. The pair of slide rails 21a and 21 b and the second connection frame 21 c are connected togetherto obtain a highly rigid H-frame. The pair of slide rails 22 a and 22 band the third connection frame 22 c are connected together to obtain ahighly rigid H-frame. For example, the pair of side frames 3 a and 3 bmove in a mutually separating direction to enable prevention of tiltingof the load cells 1. According to the present invention, it is possibleto provide the passenger's weight measurement device capable ofpreventing interferences with load measurement of the load cells withoutincreasing the number of components and without greatly changing theframework of the conventional seat structure.

According to the passenger's weight measurement device of the presentinvention, it is possible to absorb manufacturing errors of the pair ofslide rails 22 a and 22 b, the four load cells 1, and the pair of sideframes 3 a and 3 b, and height-direction accumulated errors of thesecomponents. Besides, it is possible to absorb horizontal accumulatederrors of these components caused by assembling.

The present invention is not limited to the first and secondembodiments. Various improvements and design changes can be made withoutdeparting from the gist of the invention.

The entire disclosure of Japanese Patent Applications No. Tokugan2005-264128 filed on Sep. 12, 2005, No. Tokugan 2005-268465 filed onSep. 15, 2005 and No. Tokugan 2005-264002 filed on Sep. 12, 2005including specification, claims, drawings and summary are incorporatedherein by reference in its entirety.

1. A passenger's weight measurement device for a vehicle seat,comprising: an upper rail disposed to be movable back and forth on alower rail fixed to a vehicle floor; a load sensor fixed on the upperrail; and a frame disposed on the load sensor and below a vehicle seat,wherein a rod extends from the load sensor to penetrate the frame and tobe inserted into an insertion hole formed in a center of a leaf spring,the leaf spring is curved into an angle shape to separate the center ofthe leaf spring from the frame, a nut is engaged with the rod on theleaf spring, and both hems of the leaf spring abut on the frame in astate that the leaf spring is fastened by the nut.
 2. The measurementdevice as claimed in claim 1, wherein a collar through which the rod isinserted penetrates the frame, the leaf spring is held between thecollar and the nut, and the leaf spring and the collar are held betweenthe nut and the load sensor.
 3. The measurement device as claimed inclaim 1, wherein the rod is inserted into the insertion hole in aposition shifted from a line segment for interconnecting the both hemsof the leaf spring when seen towards an inserting direction of the rod.4. The measurement device as claimed in claim 1, wherein holes areformed in the both hems of the leaf spring, and a part of a covercovering the both hems of the leaf spring is inserted into the holes. 5.An attachment structure for attaching a load sensor to a frame disposedbelow a vehicle seat, wherein a rod extends from the load sensor topenetrate the frame and to be inserted into an insertion hole formed ina center of a leaf spring, the leaf spring is curved into an angle shapeto separate the center of the leaf spring from the frame, a nut isengaged with the rod on the leaf spring, and both hems of the leafspring abut on the frame in a state that the leaf spring is fastened bythe nut.
 6. The attachment structure as claimed in claim 5, wherein acollar through which the rod is inserted penetrates the frame, the leafspring is held between the collar and the nut, and the leaf spring andthe collar are held between the nut and the load sensor.
 7. Theattachment structure as claimed in claim 5, wherein the rod is insertedinto the insertion hole in a position shifted from a line segment forinterconnecting the both hems of the leaf spring when seen towards aninserting direction of the rod.
 8. The attachment structure as claimedin claim 5, wherein holes are formed in the both hems of the leafspring, and a part of a cover covering the both hems of the leaf springis inserted into the holes.
 9. A passenger's weight measurement devicefor a vehicle seat, comprising: a pair of left and right upper railsdisposed to be movable back and forth on a pair of left and right lowerrails fixed to a vehicle floor; four load sensors fixed on front andrear sides of the pair of upper rails; and a frame disposed on the fourload sensors and below the vehicle seat, wherein two of the four loadsensors, which are arranged on one diagonal line, are set to play inback-and-forth and left-and-right directions with respect to the frame,and the other two load sensors arranged on the other diagonal line arefixed in back-and-forth and left-and-right directions with respect tothe frame.
 10. A passenger's weight measurement device for a vehicleseat, comprising: a pair of slide rails arranged in a vehicle floor; apair of side frames for supporting the seat; and load cells disposed atfour corners of the pair of slide rails and the pair of side frames,wherein the pair of side frames constitute a rectangular seat frame witha set of first connection frames for connecting both ends the pair ofside frames extending in parallel so as to be perpendicular to the pairof side frames.
 11. The measurement device as claimed in claim 10,wherein in the pair of slide rails, a pair of first slide rails and apair of second slide rails are connected so as to be slidable,respectively, the pair of first slide rails extend in parallel to befixed to the vehicle floor side, and the pair of first slide railscomprise a second connection frame for connecting middle parts of thepair of first slide rails so as to be perpendicular to the first sliderails.
 12. The measurement device as claimed in claim 11, wherein thefour load cells are arranged at four corners of the pair of second sliderails, and the pair of second slide rails extend in parallel, andcomprises a third connection frame for connecting middle parts of thepair of second slide rails so as to be perpendicular to the second sliderails.
 13. The measurement device as claimed in claim 10, wherein a pairof load cells located on one diagonal line among the four load cells areconnected to be movable up and down with respect to the seat frame, anda pair of load cells located on the other diagonal line are connected tobe movable up and down and play with respect to the seat frame.
 14. Themeasurement device as claimed in claim 10, wherein in the set of firstconnection frames, one of the first connection frames is connected toends of the pair of side rails so as to be easily deformed by shockhaving a predetermined or more strength.
 15. The measurement device asclaimed in claim 11, wherein the load cell comprises a male screw in oneend and a flange in the other end located to face opposite to the oneend, in the seat frame, four holes are formed to insert the male screwscorresponding to an arrangement of the four load cells, the pair ofsecond slide rails are fixed to the flanges, first elastic bushes areinserted into a pair of first holes located on one diagonal line amongthe four holes, a first collar is elastically disposed between the firstelastic bush and the male screw, a plain washer and a conical springwasher are mounted on the first collar, and a nut is fastened to themale screw, in a region of the seat frame, which is engaged with thepair of male screws located on the one diagonal line, an up-and-downmoving amount is regulated by a length of the first collar in an axialdirection, and the conical spring washer presses the seat frame to theload cell side.
 16. The measurement device as claimed in claim 15,wherein second elastic bushes are inserted into a pair of second holeslocated on the other diagonal line among the four holes, a second collaris inserted after a plain washer is inserted into the male screw, thesecond elastic bush is disposed to play in the second collar, a conicalspring washer are mounted on the second collar, and a nut is fastened tothe male screw, in a region of the seat frame, which is engaged with thepair of male screws located on the other diagonal line, an up-and-downmoving amount is regulated by a length of the second collar in an axialdirection, and the conical spring washer presses the seat frame to theload cell side.
 17. The measurement device as claimed in claim 15,wherein an inner diameter of the first elastic bush is formed in aconical body, and an inner periphery of an upper bottom surface of theconical body having a small radius abuts on an outer periphery of thefirst collar.